A switching device of this nature has been disclosed in U.S. Pat. No. 4,225,748. That device comprises, essentially, a housing divided into two interfitting members, one of them forming a receptacle for a circuit unit which is covered by the other member and which has an end aperture traversed by a cable leading to an external power supply. Representative circuit arrangements for such a unit are disclosed in U.S. Pat. No. 4,193,023 and others mentioned therein.
The various components of a circuit unit of this type are advantageously mounted on a carrier in the form of a dielectric film and have connecting leads represented by conductor strips printed on that film. In the interest of a compact assembly it is desirable to minimize the separation of these circuit elements on the carrier surface, yet there are mechanical and electrical limits to the packing density that can be achieved.